The invention relates to a cylinder-piston unit of a needle-free injector, with at least one cylinder accommodating an injection solution, at least one piston, and an adhesive coating arranged in the area of the free end face of the cylinder.
DE 10 2005 054 600 discloses a cylinder-piston unit of a needle-free injector, of which the cylinder has, at its front end face, a sealing film fixed by means of a pressure-sensitive adhesive The pressure-sensitive adhesive has a greater affinity to the end face of the cylinder than to the sealing film, such that, after the sealing film has been pulled off, the pressure-sensitive adhesive remains in place in order, during the injection, to fix the skin of the patient with respect to the injector.
DE 698 36 594 T3 describes a device for transcutaneous placement of a flexible cannula at a medicament admission site on the patient. For this purpose, the device has an adapter set, and a spring accumulator that can be tensioned and that is accommodated in a housing. The adapter set, which can be inserted from the front into the housing, is principally composed of an adhesion plate, a flexible cannula and an insertion needle. When the device is triggered, the adapter set is positioned on the skin by means of the relaxation of the spring accumulator. The cannula is pushed under the skin with the aid of the insertion needle. After the housing has been removed and the insertion needle pulled out, the infusion can begin.
In needle-free injections, the injection solution must be administered by a high-velocity jet through the skin of the patient. The upper layer of the skin constitutes a strong mechanical covering of the skin layers lying below it and protects them from external influences. It is composed of keratinized cells which lie alongside and over one another, the interstices being lined by lipids.
In the context of a modular injector, the object of the present invention is therefore to develop a cylinder-piston unit whose discharge system is suitable for safely penetrating the outer layers of skin covered by the term “dermis”, or possibly also the other layers, in order to convey the injection solution into or under the skin and keep it there for a definable period of time.